[Devel] [RFC PATCH vz9 5/5] ploop: convert wait_list and wb_batch_llist to use lockless lists

[Denis V. Lunev]

On 10/9/24 18:18, Alexander Atanasov wrote:
> On 9.10.24 19:09, Denis V. Lunev wrote:
>> On 10/7/24 13:12, Alexander Atanasov wrote:
>>> Convert to lockless lists - intermix with regular list due to
>>> that next pointer in both list_head and llist_head is the first
>>> field, and prev is not used. Do this so we can make babysteps
>>> forward.
> [cut]
>> I observe
>> [w(1)][52.5%][w=644MiB/s][w=165k IOPS][eta 00m:28s] <- 1 thread, 
>> partition
>> 1 (f=1): [w(1)][15.0%][w=715MiB/s][w=183k IOPS][eta 00m:51s] <- 
>> thread device
>> [w(12)][25.0%][w=1376MiB/s][w=352k IOPS][eta 00m:45s] <- 12 threads
>>
>>
>> Do we expect to have a difference right now?
>
>
> These are minor and preparations - converted lists are about metadata 
> writeback only.
> I expect improvement when the use of deferred lock is 
> eliminated/reduced to minimum which will happen when the rest of the 
> lists are converted, i.e. when all pios are moved lockless and 
> contention is reduced.
>
>
but I expect at least marginal improvement in single
thread once we have stable mappings, which has not been
happened.

Den